Single Cell Point To Multipoint (SC-PTM) is a multicast transmission technology. In SC-PTM, a base station needs to send multicast service data only to a cell that includes user equipment (UE) in an area covered by the base station, without a need to send multicast service data to a cell that does not include UE.
As shown in FIG. 1, an SC-PTM architecture includes: a broadcast/multicast service center (BM-SC) 110, an MBMS gateway (MBMS-GW) 120, a mobility management entity (MME) 130, a multi-cell/multicast coordination entity (MCE) 140, a base station 150, and UE 160. The BM-SC 110 is connected to the MBMS-GW 120. The MBMS-GW 120 is separately connected to the MME 130 and the base station 150. In addition, the MME 130 is separately connected to the MCE 140 and the base station 150, and the MCE 140 is further connected to the base station 150. The base station 150 manages one or more cells (not shown in the figure). The base station 150 can wirelessly communicate with the UE 160 in the cell.
Referring to FIG. 2, due to space constraints, the BM-SC 110 is omitted in FIG. 2. It is assumed that the MCE 140 manages a base station 1 and a base station 2, the base station 1 manages a cell 1, a cell 2, and a cell 3, and the base station 2 manages a cell 4, a cell 5, and a cell 6. The cell 1, the cell 2, the cell 3, the cell 4, and the cell 5 are cells for which a multicast service needs to be started. The BM-SC 110 sends a first multicast service session start (e.g. MBMS Session Start) message to the MBMS-GW 120. The first multicast service session start message includes identifiers of the cells 1 to 5 that are managed by the MBMS-GW 120 and for which a multicast service session needs to be started. After receiving the first multicast service session start message, the MBMS-GW 120 generates a second multicast service session start message according to the identifiers of the cells in the first multicast service session start message, and sends the second multicast service session start message to the MME 130. The second multicast service session start message includes the identifiers of the cells 1 to 5 that are managed by the MME 130 and for which a multicast service session needs to be started. After receiving the second multicast service session start message, the MME 130 generates a third multicast service session start message according to the identifiers of the cells in the second multicast service session start message, and sends the third multicast service session start message to the MCE 140. The third multicast service session start message includes the identifiers of the cells 1 to 5 that are managed by the MCE 140 and for which a multicast service session needs to be started. After receiving the third multicast service session start message, the MCE 140 generates a fourth multicast service session start message and a fifth multicast service session start message respectively for the base station 1 and the base station 2. The fourth multicast service session start message includes identifiers of the cells 1 to 3 that are managed by the base station 1 and for which a multicast service session needs to be started, and the fifth multicast service session start message includes identifiers of the cells 4 and 5 that are managed by the base station 2 and for which a multicast service session needs to be started. After receiving the fourth multicast service session start message, the base station 1 starts a multicast service for the cells 1 to 3 according to the identifiers of the cells 1 to 3 in the fourth multicast service session start message. If the multicast service is successfully started for one or more of the cells 1 to 3, the base station 1 returns a multicast service session start response (e.g. MBMS Session Start RSP) message to the MCE 140; if the multicast service fails to be started for all the cells 1 to 3, the base station 1 returns a multicast service session start failure (e.g. MBMS Session Start failure) message to the MCE 140. After receiving the fifth multicast service session start message, the base station 2 performs processing similar to that performed by the base station 1, and details are not described herein. If the MCE 140 receives the multicast service session start response messages returned by the base station 1 and/or the base station 2, the MCE 140 returns a multicast service session start response message to the MME 130; if the MCE 140 receives the multicast service session start failure messages returned by the base station 1 and the base station 2, the MCE 140 returns a multicast service session start failure message to the MME 130. If the MME 130 receives the multicast service session start response message, the MME 130 sends a multicast service session start response message to the MBMS-GW 120; if the MME 130 receives the multicast service session start failure message, the MME 130 sends a multicast service session start failure message to the MBMS-GW 120. If the MBMS-GW 120 receives the multicast service session start response message, the MBMS-GW 120 sends a multicast service session start response message to the BM-SC 110; if the MBMS-GW 120 receives the multicast service session start failure message, the MBMS-GW 120 sends a multicast service session start failure message to the BM-SC 110.
Therefore, in the prior art, the MCE 140 receives only one multicast service session start response message, regardless of a quantity of cells that are managed by the MCE 140 and for which a multicast service is successfully started, and the MCE 140 cannot know a specific cell that is managed by the MCE 140 and for which a multicast service is successfully started, or a specific cell that is managed by the MCE 140 and for which a multicast service fails to be started.